Subscriber&#39;s telephone instruments



R. E. c. BROWN 3,387,102

June 4, 1968 SUBSCRIBER'S TELEPHONE INSTRUMENTS 2 Shets-Sheet 1 Filed Nov. 27, 1964 June 4, 1968 R. E. c. BROWN SUBSCRIBER'S TELEPHONE INSTRUMENTS 2 Sheets-Sheet 2 Filed Nov. 27, 1964 UHUUUHUU 3,387,102 SUBSCRIBERS TELEPHONE INSTRUMENTS Ronald Ernest Charles Brown, Orpington, England, assignor to Associated Electrical Industries Limited, London, England, a British company Filed Nov. 27, 1964, Ser. No. 414,137

, Claims priority, application Great Britain, Nov. 29, 1963,

47,270/ 63 3 Claims. (Cl. 179-165) ABSTRACT OF THE DISCLOSURE This invention relates to subcribers telephone instruments and more particularly to gravity switches therefor.

In more recent designs of subscribers telephone instruments there is employed the principle of tone calling using a transducer which necessitates the inclusion in the gravity switch of the instrument of contacts additional to those normally required. The provision of these additional contacts tends to increase the fault liability of the instrument as there are now more contacts than hitherto in respect of which a fault can arise.

With a view to increasing the reliability of a gravity switch the present invention proposes the inclusion therein of magneti-sable reed contacts, instead of the usual mechanically actuated contacts, which are operable by a magnetic field under the control of the gravity mechanism of the switch.

In carrying out the invention the reed contacts may be operable by the magnetic field produced by a permanent magnet which is movable by means of the gravity mechanism into and out of an opera-ting position in which it magnetises the reed contacts to cause operation thereof. Alternatively, the permanent magnet may be permanently at such an operating position and there may be provided a shield of magnetic material movable under control of the gravity mechanism between a shielding position in which it lies between the permanent magnet and the reed contacts to cause the flux of the magnet to be diverted away from the reed contacts, and a second position at which it allows operation of the contacts by the magnet flux. This latter arrangement has the advantage that the gravity mechanism is only required to move the mass of the shield which would be appreciably less than that of the permanent magnet. As another alternative, a permanent magnet may be mounted for angular movement under the control of the gravity mechanism into and out of an operating position in which it magnetises the reed contacts to cause operation thereof. The magnetisable reed contacts used for the invention may be of the wellknown sealed reed contact unit kind or, particularly in the case when the permanent magnet is mounted for angular movement, they may be unsealed reed contacts mounted in an open frame.

In order that the invention may be more fully understood reference will now be made by way of example to the accompanying drawings, in which:

United States Patent FIG. 1 shows diagrammatically a section through a gravity switch provided with sealed reed contact units in conformity with the invention,

FIG. 2 is a section of FIG. 1 taken through the line AA;

FIG. 3 shows a modification of FIG. 1; and

FIGS. 4 to 6 show fragmentary details of an alternative form of gravity switch.

Referring to the drawings, a gravity switch 1 is mounted on a base plate 2 of a telephone instrument casing by means of support pillars 3 and 4. Fragmentary portions of the telephone instrument casing are indicated at 5 and 6. The gravity switch 1 has an insulating plate 7 secured to the support pillars 3 and 4 and there is mounted on this plate 7 two upstanding guide pins 8 and 9 and a sealed reed contact unit assembly 10. The upper portions 8a and 9a of the two guide pins 8 and 9 are of reduced diameter and carry respective restoring springs 11 and 12. These two restoring springs 11 and 12 support a movable platform 13 at a central recessed position on which is mounted a permanent magnet 14. Plungers 15 and 16 of the telephone instrument which extend through the casing portions 5 and 6, respectively, and are depressed downwards in well-known manner under the Weight of a telephone handset of the instrument, 'bear against the movable platform 13 to move it downwards (to the position indicated in dotted lines) when the handset is in position on the casing. When the handset is removed, the restoring springs 11 and 12 urge the movable platform 13 upwards to the position shown. Stops 17 and 18 located at the tops of the guide pins 8 and 9 retain the restoring springs 11 and 12 on these guide pins and determine the uppermost position of the movable platform 13. The sealed contact reed unit assembly 10 has a central pillar 19 around which a plurality of scaled reed contact units 20 are mounted vertically between the insulating plate 7 and a retaining disc 21. Connections 22 and 23 are soldered to terminals at opposite ends of the reed contact units 20.

When the handset of the telephone instrument is in position, the movable platform 13 is in the lower position as shown in dot-ted lines. In this position, the flux produced by the permanent magnet 14 has no effect on the need contact units 26, the normally open contacts of which therefore remain open. However, upon removal of the handset, the permanent magnet 14 is moved upwards by the platform 13 to a position adjacent the contact ends of the reed contacts. In this position, the flux from the magnet magnetises the reed contacts, thus causing them to close.

In the modification of FIG. 1 shown in FIG. 3, the permanent magnet 14 is fixed at what was the uppermost position in FIG. 1 so that its flux tends to act on the reed contacts the whole time to cause them to close. However, there is now mounted on the platform 13 a shield 14' of magnetic material which in a shielding position as shown is disposed between the permanent magnet 14 and the reed contacts to cause the flux of the magnets to be diverted away from the contacts so that the latter remain unoperated. This corresponds to the unoperated condition of the gravity switch which, as aforesaid, is brought about when the handset is in position on the telephone casing. When the handset is removed, the movable platform 13 moves upwards as before, but in this instance the shield 14' is moved from between the magnet 14 and the reed contacts 20 so allowing the latter to close due to the flux from the magnet 14.

In the alternative arrangement which is illustrated in the fragmentary details of FIGS. 4 to 6, there is provided a non-magnetic mounting frame 24 (e.g., of cast resin) from opposite sides of which cooperating pairs of magnetisable reed contacts 25 extend into the central region of the frame. There is pivotally mounted on the frame 24 at one side of the reed contacts 25 a permanent magnet 26 which extends lengthwise along the frame transversely of the reed contacts. The pivot for the permanent magnet 26 is a spindle 27 to opposite ends of which are secured respective lever arms 28 and 29. The ends of these lever arms 28 and 29 away from the spindle 27 have plungers 30 and 31 of the telephone instrument bearing against them and a restoring spring 32 wound on the spindle 27 at one end tends to rotate the spindle 27 in a clockwise direction so as to urge these ends of the lever arms 28 and 29 against the plungers 30 and 31. The permanent magnet 26 is magnetised in a direction normal to its longitudinal axis so that north and south poles of the mag net exist along opposite side faces thereof. When the telephone handset is resting on the plungers 30 and 31, the lever arms 28 and 29 have rotated the magnet 26 to a quiescent position in which its direction of magnetisation is perpendicular to the reed contacts 25 so that the flux of the magnet is unable to operate the contacts. On the other hand, when the telephone handset is removed from the plungers 3t) and 31, the restoring spring 32 rotates the magnet 26 to an angular position in which its direction of magnetisation lies parallel to the reed contacts 25 so that the contacts are now magnetised and operated.

With the arrangement of FIGS. 4 to 6, it would be possible to extend the mounting frame 24 and provide therein on the other side of the magnet 26 another line of cooperating pairs of reed contacts on which the magnet 26 would act in the same way as it acts on the other reed contacts.

A gravity switch conforming to the invention provides a relatively large number of contacts which can be used, as necessary, in the telephone instrument circuit. Moreover, where the contacts are sealed and so free from contamination by atmosphere, dust, etc., an overall improvement in reliability of the telephone instrument can be expected as compared with telephone instruments using existing gravity switches in which the contacts are mechanically actuated and are open to atmosphere.

Furthermore, gravity switches providing mechanical actuation of the contacts must be designed so that the weight of the handset is suflicient to operate the contacts satisfactorily, even when additional contacts, such as required for tone sounding or plan working instruments, are provided. With the advent of lightweight handsets, this has presented a problem that can only be resolved by providing additional ballast weight in the handset, so that the facility of using a lightweight handset is largely lost to the user. However, with the present invention, the contact operating force is magnetic and not mechanical and does not have to be increased as the number of contacts to be operated increases. Therefore, a lightweight handset can be used without the need for, or at least requiring less, ballast weight in the handset.

I claim:

1. In a subscribers telephone instrument a gravity switch comprising:

a gravity mechanism,

magnetisable reed contacts,

magnetic field producing means controllable by said gravity mechanism to cause operation of said reed contacts, characterised in that:

said magnetic field producing means is a permanent magnet,

means are provided for mounting said permanent magnet in an operating position at which it can magnetise said reed contacts to cause operation thereof,

said gravity switch also includes a shield of magnetic material,

means are provided for moving said shield under control of said gravity mechanism between a shielding position in which it lies between said permanent magnet and said reed contacts to cause the magnetic flux of said permanent magnet to be diverted away from said reed contacts, and a second position at which it allows operation of said reed contacts by said magnetic flux.

2. A gravity switch according to claim 1, wherein:

said reed contacts comprise a plurality of scaled reed contact units,

said permanent magnet is an annular permanent magnet through which said contact units extend and which is located at said operating position, and

said shield of magnetic material is an annular shield mounted for movement lengthwise of said contact units under control of said gravity mechanism between said shielding and second positions.

3. In a subscribers telephone instrument a gravity switch comprising:

a gravity mechanism,

magnetisable reed contacts, and

magnetic field producing means controllable by said gravity mechanism to cause operation of said reed contacts, characterised in that:

said reed contacts are arranged side-by-side in a line,

said magnetic field producing means is a permanent magnet of elongate form having side faces which extend along one side of said line of reed contacts, said permanent magnet being magnetised in a direction normal to its longitudinal axis so that north and south poles of the magnet exist along opposite ones of its side faces, and

means are provided for pivotally mounting and for coupling said permanent magnet to said gravity mechanism for angular movement under control of the latter between an operating position in which its direction of magnetisation lies parallel to said reed contacts so that they are magnetised and operated, and a second position in which said direction is perpendicular to said reed contacts and the flux of said magnet is thereby unable to operate them.

References Cited UNITED STATES PATENTS 2,304,061 12/1942 Little 179-164 2,322,851 6/1943 Kalb 179159 3,283,274 11/1966 De Falco 335-206 WILLIAM C. COOPER, Primary Examiner. 

